Hypertension is one of the major cardiovascular diseases in humans. To date, only one animal model has been established for this desease, that is, the Okamoto-Aoki spontaneous hypertensive rat. There are several rat su bspecies which have been shown to have genetic or salt-dependent hypertension. All of these rat models for hypertension may not completely mimic essential hypertension in the human. We have been inbreeding the Golden Syrian hamster (Mesocricetus auratus) and we find that two strains characterized by their phenotypic traits develop (8=12 wks) and maintain (1-2 yrs) an elevated arterial blood pressure. Thus, one aim of this proposal is to continue the development of these strains of spontaneously hypertensive hamsters (SHH). Another aim of this proposal is to characterize the central hemodynamics and the renin-angiotensin system in this new model of hypertension and to compare these same measurements with the renovascular model of hypertension in the hamster. In most forms of hypertension, alterations in the controlling mechanisms for blood pressure and flow in small blood vessels (microcirculartion) either lead to the development and/or maintenance of the elevated blood pressure. Thus, one major aim of this proposal is to study the microvasculature in the SHH by investigating hormonal, neural, and autoregulatory controlling mechanisms for blood pressure and flow. Since vascular lesions are a major problem in hypertension, we intend to describe the membrane transport characteriscs of the microvasculature in normal and hypertensive hamsters. Another aim of this proposal is to continue our studies on microcirculatory control mechanisms and transport characteristics in the renovascular model of hypertension in hamsters and to compare these measurements with those in the SHH. This combination of macrocirculatory and microcirculatory studies will enable us to descraibe the relative contributions of the microvessels to the developmental and maintenance phases of hypertension in these two models. Future goals relate to the possible establishment of the spontaneously hypertensive hamster as a model for the study of essential hypertension the the human. Basic information concerning microvascular transport and control of microcirculatory hemodynamics will be obtained and hopefully provide new insights into these physiological processes in normal and hypertensive states.